/*
 * @(#)AttributeFinderModule.java
 *
 * Copyright 2003-2004 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistribution of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 * 
 *   2. Redistribution in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
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package org.wso2.balana.finder;

import org.wso2.balana.ctx.EvaluationCtx;

import org.wso2.balana.attr.BagAttribute;

import org.wso2.balana.cond.EvaluationResult;

import java.net.URI;

import java.util.Set;

import org.w3c.dom.Node;

/**
 * This is the abstract class that all <code>AttributeFinder</code> modules
 * extend. All methods have default values to represent that the given feature
 * isn't supported by this module, so module writers needs only implement the
 * methods for the features they're supporting.
 * 
 * @since 1.0
 * @author Seth Proctor
 */
public abstract class AttributeFinderModule {

	/**
	 * Returns this module's identifier. A module does not need to provide a
	 * unique identifier, but it is a good idea, especially in support of
	 * management software. Common identifiers would be the full package and
	 * class name (the default if this method isn't overridden), just the class
	 * name, or some other well-known string that identifies this class.
	 * 
	 * @return this module's identifier
	 */
	public String getIdentifier() {
		return getClass().getName();
	}

	/**
	 * Returns true if this module supports retrieving attributes based on the
	 * data provided in an AttributeDesignatorType. By default this method
	 * returns false.
	 * 
	 * @return true if retrieval based on designator data is supported
	 */
	public boolean isDesignatorSupported() {
		return false;
	}

	/**
	 * Returns true if this module supports retrieving attributes based on the
	 * data provided in an AttributeSelectorType. By default this method returns
	 * false.
	 * 
	 * @return true if retrieval based on selector data is supported
	 */
	public boolean isSelectorSupported() {
		return false;
	}

	/**
	 * Returns a <code>Set</code> of <code>String</code>s that represent which
	 * AttributeDesignator categories are supported (eg, Subject, Resource,
	 * etc.), or null meaning that no particular types are supported. A return
	 * value of null can mean that this module doesn't support designator
	 * retrieval, or that it supports designators of all types. If the set is
	 * non-null, it should contain the values specified in the
	 * <code>AttributeDesignator</code>
	 * 
	 * @return a <code>Set</code> of <code>Integer</code>s, or null
	 */
	public Set<String> getSupportedCategories() {
		return null;
	}

	/**
	 * Returns a <code>Set</code> of <code>URI</code>s that represent the
	 * attributeIds handled by this module, or null if this module doesn't
	 * handle any specific attributeIds. A return value of null means that this
	 * module will try to resolve attributes of any id.
	 * 
	 * @return a <code>Set</code> of <code>URI</code>s, or null
	 */
	public Set getSupportedIds() {
		return null;
	}

	/**
	 * This is an experimental method that asks the module to invalidate any
	 * cache values it may contain. This is not used by any of the core
	 * processing code, but it may be used by management software that wants to
	 * have some control over these modules. Since a module is free to decide
	 * how or if it caches values, and whether it is capable of updating values
	 * once in a cache, a module is free to intrepret this message in any way it
	 * sees fit (including igoring the message). It is preferable, however, for
	 * a module to make every effort to clear any dynamically cached values it
	 * contains.
	 * <p>
	 * This method has been introduced to see what people think of this
	 * functionality, and how they would like to use it. It may be removed in
	 * future versions, or it may be changed to a more general message-passing
	 * system (if other useful messages are identified).
	 * 
	 * @since 1.2
	 */
	public void invalidateCache() {

	}

	/**
	 * Tries to find attribute values based on the given designator data. The
	 * result, if successful, must always contain a <code>BagAttribute</code>,
	 * even if only one value was found. If no values were found, but no other
	 * error occurred, an empty bag is returned. This method may need to invoke
	 * the context data to look for other attribute values, so a module writer
	 * must take care not to create a scenario that loops forever.
	 * 
	 * @param attributeType
	 *            the datatype of the attributes to find
	 * @param attributeId
	 *            the identifier of the attributes to find
	 * @param issuer
	 *            the issuer of the attributes, or null if unspecified
	 * @param category
	 *            the category of the attribute whether it is Subject, Resource
	 *            or any thing
	 * @param context
	 *            the representation of the request data
	 * 
	 * @return the result of attribute retrieval, which will be a bag of
	 *         attributes or an error
	 */
	public EvaluationResult findAttribute(URI attributeType, URI attributeId,
			String issuer, URI category, EvaluationCtx context) {
		return new EvaluationResult(BagAttribute.createEmptyBag(attributeType));
	}

	/**
	 * Tries to find attribute values based on the given selector data. The
	 * result, if successful, must always contain a <code>BagAttribute</code>,
	 * even if only one value was found. If no values were found, but no other
	 * error occurred, an empty bag is returned. This method may need to invoke
	 * the context data to look for other attribute values, so a module writer
	 * must take care not to create a scenario that loops forever.
	 * 
	 * @param contextPath
	 *            the XPath expression to search against
	 * @param attributeType
	 *            the datatype of the attributes to find
	 * @param contextSelector
	 *            the selector to find the context to apply XPath expression if
	 *            this is null, applied for default content. This is only used
	 *            with XACML 3.0
	 * @param root
	 *            the DOM node that XPath evaluation is done. this only used by
	 *            XACML 3.0 this can be null, if other XACML versions are used.
	 * @param context
	 *            the representation of the request data
	 * @param xpathVersion
	 *            the XPath version to use
	 * 
	 * @return the result of attribute retrieval, which will be a bag of
	 *         attributes or an error
	 */
	public EvaluationResult findAttribute(String contextPath,
			URI attributeType, String contextSelector, Node root,
			EvaluationCtx context, String xpathVersion) {

		return new EvaluationResult(BagAttribute.createEmptyBag(attributeType));
	}

}
